Working cylinder for power tool with piston lubricating system

ABSTRACT

A fastener driving tool with a working cylinder and a piston, the piston outer surface having a lubricant-saturated foam material that stores and dispenses lubricant into the piston-cylinder wall interface, thereby increasing the performance and lifespan of the tool. Another embodiment discloses a two-part piston in which the bottom portion is made of metal and absorbs the main mechanical loading forces of the piston drive and return strokes, and the top portion is made of a non-metallic material that has surfaces that act as sliding bearings against the inner wall of the cylinder.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to provisional patentapplication Ser. No. 62/746,941, titled “WORKING CYLINDER FOR POWER TOOLWITH PISTON LUBRICATING SYSTEM,” filed on Oct. 17, 2018.

TECHNICAL FIELD

The technology disclosed herein relates generally to fastener drivingtools and is particularly directed to such tools of the type which usepressurized air to drive a piston that, in turn, causes a driver bladeto force a fastener into a target workpiece. Embodiments arespecifically disclosed which use lubricant-saturated porous media, suchas a foam material, surrounding a portion of the outside of a piston,inside a working cylinder, to continually lubricate and clean the pistonand working cylinder, enhancing the performance over a greater lifetimeof the tool.

In a second embodiment fastener driving tool, the lubricant-saturatedporous media (e.g., foam material) has a first portion above a seal, anda second portion below a seal. This “double” foam material improves thelubrication below the seal, and also cleans beneath the seal.

In a third embodiment, a two-part piston is mechanically attached to adriver assembly for a fastener driving tool. The upper portion of thepiston is made of a non-metallic material and serves as guidancebearings against the cylinder wall that will not scratch the surface ofthe anodized cylinder wall. The guidance bearings are very beneficial inmaintaining the position of the piston during a drive and return stroke.A rubber seal serves as the sealing surface. A lower portion of thepiston is metal, which is capable of withstanding the stressesassociated with the impact and other forces during the drive and returnstrokes. This lower portion is rigidly attached to the driver so thatrocking and other changes in position of the driver are minimized.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

BACKGROUND

Many conventional fastener driving tools use a piston to move a driverblade that forces a nail or staple into a target workpiece, as part oftheir operational cycle. These pistons are typically driven bypressurized gas, or in some cases, by combustion air. In a product lineof pressurized gas tools known as FUSION® that are sold by Kyocera SencoIndustrial Tools, Inc., pressurized gas is stored in a main storagechamber and that gas is not vented to atmosphere, but instead is re-usedmultiple times, and can drive multiple driving strokes (includingoperational cycle counts in the tens of thousands, per charge ofpressurized gas).

One of the challenges is to provide a lubricated surface between thepiston and the inner cylinder wall to reduce friction, wear, andeventual loss of charge pressure. This surface is difficult to lubricateduring the life of the tool due to the fact that the main storagechamber and the working cylinder are sealed. The motion of the pistontends to wipe the lubricant off the sliding surfaces over time, whichthen begins to wear the sealing surface. Such a worn sealing surface canresult in pressure loss, as the charge of air escapes past the sealingsurface.

In a conventional FUSION® tool sold by Kyocera Senco, such asillustrated in FIG. 8, a working cylinder portion 205 of the tool, has amovable piston subassembly 210. The tool has a main storage chamber 274,exhibiting an outer pressure vessel wall 278. Within the main storagechamber is a working cylinder 271, and the working cylinder exhibits acylinder wall 270. Inside the cylinder wall 270 is a movable piston 280,and above the piston is a gas pressure chamber 276, whereas below thepiston is a venting chamber 275 (in this view of FIG. 8).

The piston 280 has a seal 286, and above the seal (in this view) is afirst slidable bearing 288, and below the seal (in this view) is asecond slidable bearing 289. Between the second slidable bearing 289 andthe seal 286 is a grease reservoir 282. The grease reservoir provideslubrication for the tool.

At the lower end of the piston 280 is an opening in which a top endportion 230 of a driver 290 is held in place by a connecting pin 232.The driver 290 exhibits driver teeth 292, and extends out of thecylinder base 296. Between the bottom of the main storage chamber 274,and the cylinder base, is a stationary piston stop 284.

The current FUSION® tool utilizes a lubricant that during manufacture isdeposited on the cylinder wall and on the piston seal. This lubricant isimportant to the operation of the tool. However, the lubricant cannot beresupplied without disassembling the tool.

Another challenge is to construct the piston with a hard material thatalso slides along the cylinder wall. The current FUSION® tool, asdepicted in FIG. 8, illustrates the piston as a solid piece of materialtypically made of metal. Piston slidable bearings 288 and 289 arenecessary to maintain the guidance of the piston during a drive andreturn stroke, without scoring the cylinder inner wall.

SUMMARY

Accordingly, it is an advantage to include a small volume or recess inthe outer perimeter of the piston of a power tool that retains a porousmedia, such as foam material, that holds and dispenses a liquidlubricant, which increases the life of the piston, cylinder, and thepiston seals.

It is another advantage to provide a lubricant used with a piston of afastener driving tool, by storing the lubricant in open cell foammaterial in a recess of the piston outer surface, in which the foamholds and continuously deposits the lubricant along the piston andcylinder wall during the life of the tool. This provides improved wearcharacteristics that result in improved pressure retention over a longertool life. The lubricant captured in the foam will tend to beconstrained regardless of tool orientation.

It is yet another advantage to provide a two-part piston that ismechanically attached to a driver assembly for a fastener driving tool.The upper material is non-metal and serves as guidance bearings againstthe cylinder wall that will not scratch the surface of the anodizedcylinder.

It is yet a further advantage to provide a piston with two separateportions of porous media, such as a foam material, for use in a fastenerdriving tool. At least the top foam portion stores and dispenseslubricant over the life of the tool. The lower foam portion acts as adebris “cleaner,” removing debris that may enter the cylinder such aswood, gypsum, metallic particles, collation tape, sand, dirt, andmoisture, or other items that are commonly found on constructionjobsites. This debris build-up is due to the underside of the pistonbeing exposed to ambient air.

Additional advantages and other novel features will be set forth in partin the description that follows and in part will become apparent tothose skilled in the art upon examination of the following or may belearned with the practice of the technology disclosed herein.

To achieve the foregoing and other advantages, and in accordance withone aspect, a piston for use in a power tool is provided, whichcomprises: a top outer surface, a bottom outer surface, and a side wallouter surface that runs between the top and bottom outer surfaces; afirst recess in the side wall outer surface of the piston; and a porousmedia positioned in the first recess along the side wall outer surfaceof the piston, the porous media containing a liquid lubricant material.

In accordance with another aspect, a piston for use in a power tool isprovided, which comprises: a top outer surface, a bottom outer surface,and a cylindrical side wall outer surface that runs between the top andbottom outer surfaces, the piston having a circular cross-section; afirst circumferential recess in the cylindrical outer surface of thepiston; and an annular porous media positioned in the firstcircumferential recess, the porous media containing a liquid lubricantmaterial.

In accordance with yet another aspect, a working cylinder for a powertool is provided, which comprises: a hollow cylinder that includes amovable two-part piston, the cylinder including a variable displacementvolume on a first side of the piston, and the cylinder including avariable venting volume on a second, opposite side of the piston; saidtwo-part piston, comprising: a first portion made of a metallic materialthat is proximal to the second side of the piston, the first portionbeing sufficiently small in outer diameter so that it does not makephysical contact with an inner surface of the hollow cylinder; a secondportion made of a non-metallic material that is proximal to the firstside of the piston, the second portion including at least one surfacethat makes slidable contact with the inner surface of the hollowcylinder, the at least one surface thereby acting as a slidable bearingsurface for the piston; the first portion and the second portion beingattached to one another in a manner such that the first and secondportions always move together as a single piston subassembly.

In accordance with still another aspect, a piston for use in a powertool is provided, which comprises: a top outer surface, a bottom outersurface, and a cylindrical side wall outer surface that runs between thetop and bottom outer surfaces, the piston having a circularcross-section; a first circumferential recess in the cylindrical outersurface of the piston; and a first annular porous media positioned inthe first circumferential recess; a second circumferential recess in thecylindrical outer surface of the piston, located at a different positionalong the cylindrical outer surface of the piston; a second annularporous media positioned in the second circumferential recess; and atleast one of the first and second annular porous media containing aliquid lubricant material.

In accordance with a further aspect, a piston for use in a power tool isprovided, which comprises: a top outer surface, a bottom outer surface,and a side wall outer surface that extends between the top and bottomouter surfaces; a first recess in the side wall outer surface of thepiston; and a porous media positioned in the first recess along the sidewall outer surface of the piston, the porous media containing a liquidlubricant.

In accordance with a yet further aspect, a working cylinder for a powertool is provided, which comprises: a hollow cylinder that includes amovable two-part piston, the cylinder including a variable displacementvolume on a first side of the piston, and the cylinder including avariable venting volume on a second, opposite side of the piston; thetwo-part piston comprising: a first portion made of a metal that isproximal to the second side of the piston, the first portion beingsufficiently small in outer width so that it does not make physicalcontact with an inner surface of the hollow cylinder; a second portionmade of a non-metal that is proximal to the first side of the piston,the second portion including at least one surface that makes slidablecontact with the inner surface of the hollow cylinder, the at least onesurface thereby acting as a slidable bearing surface for the piston; andthe first portion and the second portion being attached to one anotherin a manner such that the first and second portions always move togetheras a single piston subassembly.

In accordance with a still further aspect, a piston for use in a powertool is provided, which comprises: a top outer surface, a bottom outersurface, and a side wall outer surface that extends between the top andbottom outer surfaces; a first recess in the side wall outer surface ofthe piston; a first porous media positioned in the first recess; asecond recess in the side wall outer surface of the piston, located at adifferent position along the side wall outer surface of the piston; asecond porous media positioned in the second recess; and at least one ofthe first porous media and second porous media containing a liquidlubricant.

Still other advantages will become apparent to those skilled in this artfrom the following description and drawings wherein there is describedand shown a preferred embodiment in one of the best modes contemplatedfor carrying out the technology. As will be realized, the technologydisclosed herein is capable of other different embodiments, and itsseveral details are capable of modification in various, obvious aspectsall without departing from its principles. Accordingly, the drawings anddescriptions will be regarded as illustrative in nature and not asrestrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thespecification illustrate several aspects of the technology disclosedherein, and together with the description and claims serve to explainthe principles of the technology. In the drawings:

FIG. 1 is a side view of a piston subassembly for use in a fastenerdriving tool, as constructed according to the principles of thetechnology disclosed herein.

FIG. 2 is a section view along the line 2-2 of FIG. 1.

FIG. 3 is a perspective view showing the driver blade and driver teethof the tool of FIG. 1.

FIG. 4 is a section view of a working cylinder of the fastener drivingtool of FIG. 1, showing the piston subassembly.

FIG. 5 is a side view of a second embodiment of a piston subassembly foruse in a fastener driving tool, as constructed according to theprinciples of the technology disclosed herein.

FIG. 6 is a section view along the line 6-6 of FIG. 5.

FIG. 7 is a perspective view of the second embodiment fastener drivingtool of FIG. 5.

FIG. 8 is a section view of a fastener driving tool known in the priorart.

FIG. 9 is a section view similar to that of FIG. 2, in which a porousmedia, such as foam material, is arranged in stacks.

FIG. 10 is a top elevational view of the foam material of FIG. 9.

FIG. 11 is a section view similar to that of FIG. 2, in which a porousmedia, such as foam material, is layered, such that an outer layercovers or surrounds an inner layer.

FIG. 12 is a top elevational view of the foam material of FIG. 11.

DETAILED DESCRIPTION

Reference will now be made in detail to the present preferredembodiment, an example of which is illustrated in the accompanyingdrawings, wherein like numerals indicate the same elements throughoutthe views.

It is to be understood that the technology disclosed herein is notlimited in its application to the details of construction and thearrangement of components set forth in the following description orillustrated in the drawings. The technology disclosed herein is capableof other embodiments and of being practiced or of being carried out invarious ways. Also, it is to be understood that the phraseology andterminology used herein is for the purpose of description and should notbe regarded as limiting. The use of “including,” “comprising,” or“having” and variations thereof herein is meant to encompass the itemslisted thereafter and equivalents thereof as well as additional items.Unless limited otherwise, the terms “connected,” “coupled,” and“mounted,” and variations thereof herein are used broadly and encompassdirect and indirect connections, couplings, and mountings. In addition,the terms “connected” and “coupled” and variations thereof are notrestricted to physical or mechanical connections or couplings.Furthermore, the terms “communicating with” and “in communications with”refer to two different physical or virtual elements that somehow passsignals or information between each other, whether that transfer ofsignals or information is direct or whether there are additionalphysical or virtual elements therebetween that are also involved in thatpassing of signals or information. Moreover, the term “in communicationwith” can also refer to a mechanical, hydraulic, or pneumatic system inwhich one end (a “first end”) of the “communication” may be the “cause”of a certain impetus to occur (such as a mechanical movement, or ahydraulic or pneumatic change of state) and the other end (a “secondend”) of the “communication” may receive the “effect” of thatmovement/change of state, whether there are intermediate componentsbetween the “first end” and the “second end,” or not.

The terms “first” and “second” preceding an element name, e.g., firstinlet, second inlet, etc., are used for identification purposes todistinguish between similar or related elements, results or concepts,and are not intended to necessarily imply order, nor are the terms“first” and “second” intended to preclude the inclusion of additionalsimilar or related elements, results or concepts, unless otherwiseindicated.

Referring now to FIG. 1, a first embodiment of a piston subassembly foruse in a fastener driving tool generally designated by the referencenumeral 10 has two main halves: a piston top 20, and a piston bottom 22.The piston top 20 is constructed of a hard plastic, or othernon-metallic material, preferably Delrin, whereas the piston bottom 22is constructed of metal, preferably aluminum. The piston bottom isconstructed with a stem that has a plurality of male threads 28, and thepiston top has a threaded opening to receive the stem, in which thethreads are female. The piston top is threadably attached using thepiston bottom's male threads (see FIG. 2), such that both piston partsmove together as a single piston subassembly 10.

It should be noted that the piston design described above is merely apreferred embodiment for constructing the overall piston, and othertwo-piece piston designs could be used without departing from theprinciples of this technology. For example, as one alternative design,the two piston halves 20 and 22 may be attached to one another throughany type of reliable mechanical connection, including a pin connector.Alternatively again, the two piston halves 20, 22 could be constrainedwithout mechanical fasteners so that they always move together.Furthermore, the gas pressure of the working cylinder 71 (see FIG. 4)will tend to keep the top piston half 20 firmly pressed against thebottom piston half 22 under almost all circumstances of tool operation.

The general shape of piston subassembly 10 includes a cylindrical outersurface which has a circular cross-section, as can be seen in FIG. 3.The center of the circular cross-section is located along a longitudinalaxis of the piston, in which that longitudinal axis can be seen at “L”on FIG. 2. It will be understood that the exact shape of the outerperimeter of the piston, and the exact shape of the corresponding innersurface of the cylinder sleeve, do not necessarily have to be preciselycircular. Instead, these surfaces could have other geometric shapes, solong as they are “mating shapes,” and still fall within the principlesof the technology disclosed herein. With regard to the disclosurepresented herein, it will be assumed that the piston indeed has acircular cross-section, and therefore, the inner surface of the cylindersleeve is also circular.

A driver 90 (see FIG. 3) has an upper attachment portion 30 that isinstalled during manufacture into an opening in the piston bottom half22. The piston bottom 22 exhibits two through openings 42 and 44 thatare transverse to the driver opening. Two connecting pins 32 and 34 areused to secure the driver, at the driver upper portion 30, to the pistonbottom 22. It will be understood that the various directionalnomenclature provided above is with respect to the illustration of FIG.2, and the first embodiment can be used in many other angular positions,without departing from the principles of this technology. The use ofthese two connecting pins 32 and 34 help to keep the piston subassembly10 aligned with the driver 90.

It will be further understood that this piston subassembly 10 isdesigned to move in a reciprocating manner along a direction that willbe referred to herein as a longitudinal axis. On FIG. 2, such alongitudinal axis is designated by the letter “L.” The connecting pins32 and 34 are placed in a perpendicular, transverse direction, which isindicated on FIG. 2 by the letter “T.”

The piston top portion 20 has two circumferential recesses or grooveslocated on the outside surface of the piston. The upper groove (orrecess) holds an annular-shaped material 24 that comprises a porousmedia such as foam, and the lower groove (or recess) holds an annularseal 26, which in this illustrated embodiment is a lobed seal. (Notethat the annular seal 26 is also sometimes referred to herein as a“perimeter seal,” since it runs around the outer perimeter of thepiston.) The porous media 24 holds a liquid lubricant material (such asMobil Vactra 2 oil, a premium ISO Viscosity Grade 68 slideway oil), andacts as a reservoir for the lubricant. The porous material can comprisevarious specific types of materials, such as an open cell foam material,or a sponge-like foam material, or an air filter material that isresistant to oil. It is preferred that the foam material is soft,flexible, and non-abrasive.

An open cell foam material works well for the purposes described herein,and it will be understood that the terms “foam” or “foam material” asused hereinafter refer to all such types of porous media that are ableto hold an appropriate liquid or grease lubricant material for use inthese power tools. It will also be understood that, for the purposes ofthis disclosure, the phrase “circumferential recess” refers to a recessor “groove” in the outer surface of the piston, for example, regardlessof the exact shape of the cross-section of that piston; in other words,the piston could have a circular or elliptical cross-section shape, oreven a square or rectangular cross-section shape, yet the recess beingreferred herein would nevertheless be referred to as a “circumferential”recess, so that these recesses are better understood by the reader ofthis disclosure.

The porous media 24 may hold a variety of alternative liquid lubricantmaterials. The liquid lubricant material type used will alter thefriction of the piston 10 during a lift cycle. It would be desirable forthis liquid lubricant to be a lightweight oil having a viscosity aroundISO 68 (about SAE 20W).

It should be noted that the “liquid” lubricant used for this purpose maycontain solid particles as a form of grease in solution with a liquid;or possibly the “liquid” lubricant used could mainly comprise anappropriate grease material (with or without solid particles) that, whenin use, acts as a semi-liquid or semi-solid material to spread out alongthe piston's surfaces as the piston undergoes reciprocating movements.

Preferably, the foam material 24 comprises open cell foam, such as areticulated urethane foam, having an average cell density of about 60-80pores per inch. The foam material should be resistant to lubricatingoils, and perhaps also to grease. Certain types of air filter materialcan be used for the foam material 24, including pre-filters used forKoehler or Briggs and Stratton lawnmower engines.

The foam 24 is in constant contact with the inner cylinder wall, slowlydispensing lubricant over the life of the tool. The seal 26 is also inconstant contact with the cylinder wall, and keeps the lubricantcontained inside the cylinder; moreover, the seal retains the high gaspressure above the piston (in the variable displacement volume 76). Thecylinder and the seal may be pre-coated with an anti-seize lubricant,such as Permatex 133A. (The anti-seize is wiped on, like a grease.) Itis to be noted that the foam 24 does not act as a seal per se, but isintended to store and dispense lubricant along the cylinder wall. Also,a second seal “above” the foam 24 is not necessary, because anylubricant that moves “above” the seal will be re-used by subsequentpiston movements.

It should also be noted that, once the tool has been fully assembled,the foam 24 becomes the sole source of the liquid lubricant for thecylinder and piston. More specifically, the foam acts as an inhibitingfactor that prevents the lubricant from being dispensed too quickly,thereby increasing the normal life of the entire tool.

Although the statement in the preceding paragraph is true for certainembodiments, alternative embodiments are envisioned where a greasematerial is used in conjunction with a liquid lubricant, and the greaseis typically not directly applied to the foam material. Instead, thegrease is applied to the inner surface of the cylinder sleeve (cylinderwall 70) before the piston is installed. An example of a suitable greasematerial is Valvoline Crimson multi-purpose grease. Another alternateexample grease lubricant material is Kluber ISOFLEX TOPAS NB 52. Yetanother alternate example is Kluber ISOFLEX TOPAS NB 152.

As discussed above, various types of lubricants may work well in thisfastener driving tool working cylinder. The liquid lubricants aregenerally to be applied to the foam 24, as discussed above. The greaselubricants are generally to be applied to the seal 26 and/or to theinner surface of the cylinder wall 70. In one alternative embodiment,both a grease material and a liquid material are simultaneously used,such as the Valvoline Crimson grease and the Mobil Vactra 2 oil.

If a grease material is to be used in the working cylinder 71, then itwould be applied to the inner surface of the cylinder before the pistonsubassembly 10 is installed therein. Furthermore, the grease can also beapplied to the seal 26, as per the tool designer's choice. If grease isused at the seal 26, that grease can be applied into the recess wherethe seal goes either before or after the seal 26 is installed onto theupper piston 20. In general, it is preferred to install the foam 24 intoits recess in the upper piston 20 before any liquid lubricant is appliedto that foam 24. (It is difficult to install a “wet” piece of foam intothat groove or recess.) Finally, it is likely better if at least some ofthe grease is applied “beneath” the seal 26—i.e., into the small spacebetween the seal and the bottom surface of the groove. The moregrease—and the more liquid lubricant—that can be “stored” in thisworking cylinder and piston combination, the longer that combinationwill properly operate.

Referring now to FIG. 4, the piston subassembly 10 is shown integratedinto a working cylinder portion of a driving tool, which is generallyreferred to by the reference numeral 5. An outer wall 78 contains a mainstorage chamber 74, in which a working cylinder 71 encloses the pistonsubassembly 10. The working cylinder portion includes a cylinder base 96that fully encloses the main storage chamber 74. A gas pressure chamber76 is contained inside the working cylinder, above the piston top 20.The gas chamber 76 contains a variable volume, or “displacement volume,”of pressurized gas that is used to drive the piston during operation.Beneath the piston bottom 22 is a cylinder “venting chamber” 75, whichvents to atmosphere.

During operation, the piston subassembly 10 slides along a cylinderinner wall (or “sleeve”) 70 of the working cylinder 71. The bearingsurfaces 52, 54, and 56 of piston top 20 contact the cylinder wall 70during normal movement. The piston bottom 22 is slightly smaller indiameter and does not contact the cylinder wall. As the pistonsubassembly slides along the cylinder wall, the piston is stopped by astationary piston stop 84.

These bearing surfaces 52, 54, and 56 are quite different than previousdesigns using metal pistons with insert bearings. In previous designs,the insert bearings provided a slidable surface along the cylinder wall,which allowed the piston to not touch the cylinder wall at all. In thisnew design, the bearing surfaces 52, 54, and 56 of the pistonsubassembly 10 actually touch and slide along the cylinder wall surface,and they act as low-friction guide bearing surfaces, as well.

The driver 90 moves with the piston subassembly 10 during operation. Thedriver exhibits driver teeth 92. The driver moves along a driver track93 through a guide body 36. The guide body 36 is mounted beneath thecylinder base 96. The guide body receives a fastener from a magazine(not shown), and guides the driver and the fastener to an exit portionof the tool, and into a workpiece. It will be understood that thevarious directional nomenclature provided above is with respect to theillustration of FIG. 4, and the first embodiment can be used in manyother angular orientations, without departing from the principles ofthis technology.

Referring now to FIG. 5, a second embodiment of a piston subassembly foruse in a fastener driving tool generally designated by the referencenumeral 110 has two main halves: a piston top 120, and a piston bottom122. The piston top 120 is constructed of a hard plastic, or othernon-metallic material, preferably Delrin, whereas the piston bottom 122is constructed of metal, preferably aluminum. The piston bottom isconstructed with a stem that has a plurality of male threads 128, andthe piston top has a threaded opening to receive the stem, in which thethreads are female. The piston top is threadably attached using thepiston bottom's male threads (see FIG. 6), such that both piston partsmove together as a single piston subassembly. It should be noted thatthe two piston halves 120 and 122 may be attached to one another throughany type of reliable mechanical connection, including a pin connectorfor example.

The general shape of piston subassembly 110 includes a cylindrical outersurface which has a circular cross-section, as can be seen in FIG. 7.The center of the circular cross-section is located along a longitudinalaxis of the piston, in which that longitudinal axis can be seen at “L”on FIG. 6. It will be understood that the exact shape of the outerperimeter of the piston, and the exact shape of the corresponding innersurface of the cylinder sleeve, do not necessarily have to be preciselycircular. Instead, these surfaces could have other geometric shapes, solong as they are “mating shapes,” and still fall within the principlesof the technology disclosed herein. With regard to the disclosurepresented herein, it will be assumed that the piston indeed has acircular cross-section, and therefore, the inner surface of the cylindersleeve is also circular.

A driver 190 (see FIG. 6) has an upper attachment portion 130 that isinstalled during manufacture into an opening in the piston bottom half122. The piston bottom 122 exhibits two through openings 142 and 144that are transverse to the driver opening. Two connecting pins 132 and134 are used to secure the driver, at the driver upper portion 130, tothe piston bottom 122. It will be understood that the variousdirectional nomenclature provided above is with respect to theillustration of FIG. 5, and the first embodiment can be used in manyother angular positions, without departing from the principles of thistechnology.

It will be again understood that this piston subassembly 110 is designedto move in a reciprocating manner along a direction that will bereferred to herein as a longitudinal axis. On FIG. 6, such alongitudinal axis is designated by the letter “L.”

The piston top 120 has three circumferential recesses or grooves locatedon the outside surface of the piston. The upper groove holds acircular-shaped material 124 that comprises a porous media, such as afoam material, and the lower groove holds another circular-shapedmaterial of porous media (e.g., foam material) 125. The middle grooveholds a circular seal 126. (Note that the annular seal 126 is alsosometimes referred to herein as a “perimeter seal,” since it runs aroundthe outer perimeter of the piston. Moreover, the porous media—or foampiece—124 is sometimes referred to herein as a “first porous media,” andthe porous media—or foam piece—125 is sometimes referred to herein as a“second porous media.”) In one embodiment, both foam pieces 124 and 125hold a lubricant, and act as a reservoir for the lubricant. Preferably,the foam 124 and 125 comprises open cell foam. The foam 124 and 125 isin constant contact with the inner cylinder wall 71, slowly dispensinglubricant over the life of the tool.

The seal 126 is also in constant contact with the cylinder, and keepsthe lubricant contained inside the cylinder. It is to be noted that thefoam pieces 124 and 125 do not act as a seal per se, but are intended tostore and dispense lubricant along the cylinder. Also, a second seal“above” the foam 124 is not necessary, because any lubricant that moves“above” the seal will be re-used. The lower foam piece 125, in additionto dispensing lubricant, also acts as a “wiper” or “catcher” forpreventing outside debris from entering the seal's region of the tool inthe area near the bottom of the cylinder 71.

In an alternate embodiment, the foam 125 does not contain lubricant.Instead, the foam mainly acts as a “wiper” or “catcher” for debris thatfinds its way into the bottom area of the working cylinder 71. Iflubricant should happen to make its way past the seal 126 to this secondfoam piece 125, then the foam piece 125 will re-distribute thatlubricant. Optionally, the second foam piece 125 can receive a “light”amount of lubricant at the time of manufacture.

The second foam material 125 in the embodiment of FIG. 6 is positioned“below” the seal 126 for a reason. As discussed above, the foam 125 actsas a “wiper” or “catcher” to keep outside debris from reaching the seal126, thereby enhancing the life of the seal 126, and thereby extendingthe life of the tool by maintaining a high air pressure in the mainstorage chamber and in the spaces “above” the top of the piston (abovethe surface 120) for a longer time.

The second foam material 125 in the embodiment of FIG. 6 also acts as a“retainer” to keep the beneficial lubricant “above” that foam piece 125;i.e., it will tend to keep the lubricant where the piston travels insidethe working cylinder. And, as such a “retainer,” the foam material 125tends to keep the lubricant from traveling “down” (in this view) to theworkpiece surface, when a fastener is driven.

It should be noted that the porous media (such as foam pieces) 24, 124,and 125 in the various embodiments disclosed herein do not need to beformed of a single piece of material. For example, the foam pieces couldbe arranged as a stack of foam pieces each having a smaller thickness,such as the pieces 61 and 63 on FIG. 9. The top annular shape of thisstack of smaller thickness foam pieces would have the shape depicted onFIG. 10.

Furthermore, the porous media (such as foam pieces) 24, 124, and 125 inthe various embodiments could be layered as different inner and outerdiameters, such as the pieces 62 and 64 on FIG. 11, in which the outerlayer 64 covers the inner layer 62. The top annular appearance of theshapes of those layered foam pieces would have the form illustrated onFIG. 12. In this configuration, the inner and outer foam pieces 62 and64 could have different physical characteristics, if desired. Forexample, the inner foam piece 62 could be selected for having an abilityto maximize a large quantity of lubricant that can be retained, whereasthe outer foam piece 64 could be selected for having a superior wickingability, which would more readily transfer lubricant from its innerdiameter to its outer diameter, and hence to the piston's outerperimeter surfaces near the cylinder inner wall.

It will be understood that the references to an inner diameter or anouter diameter of the hollow cylinder or of the piston, seal, or foampieces can be referred to by other words, such as an inner (or outer)width, or an inner (or outer) dimension, while referring to the same ora similar portion of the parts that make up the power tool designdisclosed herein. This is especially true if the piston and workingcylinder are not perfectly round in shape. For example, the piston'souter shape (in cross-section) and the working cylinder's inner shape(in cross-section) could be elliptical, rather than circular, ifdesired.

It will be further understood that the description of the piston 10 inFIG. 4, or the piston 110 in FIG. 6, for example, could be described ashaving “a top outer surface, a bottom outer surface, and a side wallouter surface that extends between the top and bottom outer surfaces,”with reference to the characteristics of the combination of the upperpiston portion 20 (in FIG. 4), the lower piston portion 22 (in FIG. 4),and the side walls 52, 54, and 56 (in FIG. 4), for example. Of course,the lower portion of the piston 22 also has side walls, which are notnumbered on FIG. 4.

Finally, it will be additionally understood that the piston subassembly10, or 110, could be constructed of a single piece of material, ifdesired by the designer of the power tool for which it will be used,without departing from the principles of the technology disclosedherein. Certain modifications would likely have to be made for that typeof piston construction, but certainly the foam pieces (porous media)used to dispense lubricant could still be included so as to provide someimportant benefits, as described herein.

The principles discussed above and illustrated in the drawings can befurther summarized in a series of short statements, such as follows:

{A1} A piston for use in a power tool, the piston comprising: a topouter surface, a bottom outer surface, and a cylindrical side wall outersurface that runs between the top and bottom outer surfaces, the pistonhaving a circular cross-section; a first circumferential recess in thecylindrical outer surface of the piston; and an annular porous mediapositioned in the first circumferential recess, the porous mediacontaining a liquid lubricant material.

{A2} The piston of the above paragraph plus the following features: asecond circumferential recess in the cylindrical outer surface of thepiston located at a different position along the outer surface of thepiston; and an annular seal positioned in the second circumferentialrecess.

{A3} The piston of the above paragraph plus the following features: ahollow cylinder having a circular inner diameter that is larger than thecylindrical outer surface of the piston; wherein: the annular porousmedia makes physical contact with the circular inner diameter of thehollow cylinder as the piston moves through the cylinder in areciprocating pattern; and the liquid lubricant material is used tolubricate a portion of the circular inner diameter of the hollowcylinder that is proximal to the cylindrical outer surface of the pistonas the piston moves through the cylinder.

{A4} The piston of the above paragraph plus the following features: theannular seal makes physical contact with the circular inner diameter ofthe hollow cylinder as the piston moves through the cylinder in areciprocating pattern; wherein: the annular seal prevents a majority ofthe liquid lubricant material from moving past the secondcircumferential recess in the cylindrical outer surface of the piston.

{A5} The cylinder with piston of the above paragraph plus the followingfeatures: a driver that is in mechanical communication with the piston;a guide body that guides the driver, and that receives a fastener to bedriven by the driver to an exit portion of the guide body.

{A6} The cylinder with piston of the paragraph {A4} plus the followingfeatures: a main storage chamber that contains a pressurized gas;wherein: the cylinder including a variable displacement volume on afirst side of the piston that is in pneumatic communication with themain storage chamber, and the cylinder including a variable ventingvolume on a second, opposite side of the piston that is in pneumaticcommunication with an outer environment; and the annular seal prevents amajority of the liquid lubricant material from moving into the outerenvironment; however, the liquid lubricant material is not preventedfrom moving toward the main storage chamber, where it will be re-used inlater operational cycles.

{A7} The cylinder with piston of the paragraph {A4} plus the followingfeatures: the porous media is the sole source of lubricant for thehollow cylinder and piston, and the tool cannot be re-supplied withadditional lubricant without disassembling the main storage chamber andhollow cylinder subassembly.

{A8} The cylinder with piston of the paragraph {A4} plus the followingfeatures: the porous media comprises open cell foam having an averagecell density of about 60-80 pores per inch.

{A9} The cylinder with piston of the above paragraph plus the followingfeatures: the foam material comprises air filter material that isresistant to lubricating oil.

{A10} The cylinder with piston of the paragraph {A4} plus the followingfeatures: the liquid lubricant comprises premium ISO Viscosity Grade 68slideway oil.

{A11} The cylinder with piston of the above paragraph plus the followingfeatures: the liquid lubricant comprises Mobil Vactra 2 oil.

{A12} The cylinder with piston of the paragraph {A3} plus the followingfeatures: the liquid lubricant comprises lubricating oil; furthercomprising an anti-seize lubricant that is applied within said cylinder.

{A13} The cylinder with piston of the above paragraph plus the followingfeatures: the anti-seize lubricant comprises Permatex 133A.

{B1} A working cylinder for a power tool, comprising: a hollow cylinderthat includes a movable two-part piston, the cylinder including avariable displacement volume on a first side of the piston, and thecylinder including a variable venting volume on a second, opposite sideof the piston; said two-part piston, comprising: a first portion made ofa metallic material that is proximal to the second side of the piston,the first portion being sufficiently small in outer diameter so that itdoes not make physical contact with an inner surface of the hollowcylinder; a second portion made of a non-metallic material that isproximal to the first side of the piston, the second portion includingat least one surface that makes slidable contact with the inner surfaceof the hollow cylinder, the at least one surface thereby acting as aslidable bearing surface for the piston; the first portion and thesecond portion being attached to one another in a manner such that thefirst and second portions always move together as a single pistonsubassembly.

{B2} The working cylinder of the above paragraph plus the followingfeatures: a first circumferential recess in the outer surface of thepiston; and a porous media positioned in the first circumferentialrecess, the porous media containing a liquid lubricant material.

{B3} The working cylinder of the above paragraph plus the followingfeature: the porous media comprises an annular foam material.

{B4} The working cylinder of the above paragraph plus the followingfeatures: the annular foam material makes physical contact with thecircular inner diameter of the hollow cylinder as the piston movesthrough the cylinder in a reciprocating pattern; and the liquidlubricant material is used to lubricate a portion of the circular innerdiameter of the hollow cylinder that is proximal to the cylindricalouter surface of the piston as the piston moves through the cylinder.

{B5} The working cylinder of the paragraph {B2} plus the followingfeatures: a second circumferential recess in the cylindrical outersurface of the piston located at a different position along the outersurface of the piston; and an annular seal positioned in the secondcircumferential recess.

{B6} The working cylinder of the above paragraph plus the followingfeatures: the annular seal makes physical contact with the circularinner diameter of the hollow cylinder as the piston moves through thecylinder in a reciprocating pattern; and the annular seal prevents amajority of the liquid lubricant material from moving past the secondcircumferential recess in the cylindrical outer surface of the piston.

{C1} A piston for use in a power tool, the piston comprising: a topouter surface, a bottom outer surface, and a cylindrical side wall outersurface that runs between the top and bottom outer surfaces, the pistonhaving a circular cross-section; a first circumferential recess in thecylindrical outer surface of the piston; and a first annular porousmedia positioned in the first circumferential recess; a secondcircumferential recess in the cylindrical outer surface of the piston,located at a different position along the cylindrical outer surface ofthe piston; a second annular porous media positioned in the secondcircumferential recess; and at least one of the first and second annularporous media containing a liquid lubricant material.

{C2} The piston of the above paragraph plus the following features: athird circumferential recess in the cylindrical outer surface of thepiston located at a different position along the outer surface of thepiston than the first and second circumferential recesses; and anannular seal positioned in the third circumferential recess.

{C3} The piston of the above paragraph plus the following feature: thefirst annular porous media comprises a first annular foam material; andthe second annular porous media comprises a second annular foammaterial.

{C4} The piston of the above paragraph plus the following features: ahollow cylinder having a circular inner diameter that is larger than thecylindrical outer surface of the piston; wherein: the first and secondannular foam material makes physical contact with the circular innerdiameter of the hollow cylinder as the piston moves through the cylinderin a reciprocating pattern; and the liquid lubricant material is used tolubricate a portion of the circular inner diameter of the hollowcylinder that is proximal to the cylindrical outer surface of the pistonas the piston moves through the cylinder.

{C5} The cylinder and piston of the above paragraph plus the followingfeatures: the annular seal makes physical contact with the circularinner diameter of the hollow cylinder as the piston moves through thecylinder in a reciprocating pattern; wherein: the annular seal preventsa majority of the liquid lubricant material from moving past the secondcircumferential recess in the cylindrical outer surface.

{C6} The cylinder and piston of the above paragraph plus the followingfeatures: the cylinder including a variable displacement volume on afirst side of the piston that is in pneumatic communication with a mainstorage chamber of pressurized gas, and the cylinder including avariable venting volume on a second, opposite side of the piston that isin pneumatic communication with an outer environment; and the annularseal prevents a majority of the liquid lubricant material from movinginto the outer environment; however, the liquid lubricant material isnot prevented from moving toward the main storage chamber, where it willbe re-used in later operational cycles.

{C7} The cylinder and piston of the above paragraph plus the followingfeatures: the first circumferential recess and the first annular foammaterial are positioned proximal to the first side of the piston; thesecond circumferential recess and the second annular foam material arepositioned proximal to the second side of the piston; and the thirdcircumferential recess and the annular seal are positioned between thefirst and second circumferential recesses along the outer surface of thepiston.

{C8} The cylinder and piston of the above paragraph plus the followingfeatures: the first annular foam material contains a liquid lubricantupon manufacture, but the second annular foam material does not containa liquid lubricant upon manufacture.

{C9} The cylinder and piston of the paragraph {C7} plus the followingfeatures: both the first and second annular foam materials contain aliquid lubricant upon manufacture.

{C10} The cylinder with piston of the paragraph {C4} plus the followingfeatures: the liquid lubricant comprises lubricating oil; furthercomprising an anti-seize lubricant that is applied within said cylinder.

{C11} The cylinder with piston of the above paragraph plus the followingfeatures: the anti-seize lubricant comprises Permatex 133A.

{D1} A piston for use in a power tool, the piston comprising: a topouter surface, a bottom outer surface, and a side wall outer surfacethat runs between the top and bottom outer surfaces; a first recess inthe side wall outer surface of the piston; and a porous media positionedin the first recess along the side wall outer surface of the piston, theporous media containing a liquid lubricant material.

{D2} The piston of the above paragraph plus the following features: ahollow cylinder having an inner dimension that is larger than the sidewall outer surface of the piston; and the porous media makes physicalcontact with the inner diameter of the hollow cylinder as the pistonmoves through the cylinder in a reciprocating pattern; wherein: theliquid lubricant material is used to lubricate a portion of the innerdiameter of the hollow cylinder that is proximal to the side wall outersurface of the piston as the piston moves through the cylinder.

{D3} The piston of the paragraph {D1} plus the following feature: saidporous media comprises a foam material.

Note that some of the embodiments illustrated herein do not have all oftheir components included on some of the figures herein, for purposes ofclarity. To see examples of such outer housings and other components,especially for earlier designs, the reader is directed to other U.S.patents and applications owned by Senco. Similarly, information about“how” the electronic controller operates to control the functions of thetool is found in other U.S. patents and applications owned by Senco.Moreover, other aspects of the present tool technology may have beenpresent in earlier fastener driving tools sold by the Assignee, KyoceraSenco Industrial Tools, Inc., including information disclosed inprevious U.S. patents and published applications. Examples of suchpublications are patent numbers U.S. Pat. Nos. 6,431,425; 5,927,585;5,918,788; 5,732,870; 4,986,164; 4,679,719; 8,011,547, 8,267,296,8,267,297, 8,011,441, 8,387,718, 8,286,722, 8,230,941, and 8,763,874;also published U.S. patent application No. 2016/0288305 and publishedU.S. patent application, No. 2018/0178361. These documents areincorporated by reference herein, in their entirety.

It will be further understood that any type of product described hereinthat has moving parts, or that performs functions (such as computerswith processing circuits and memory circuits), should be considered a“machine,” and not merely as some inanimate apparatus. Such “machine”devices should automatically include power tools, printers, electroniclocks, and the like, as those example devices each have certain movingparts. Moreover, a computerized device that performs useful functionsshould also be considered a machine, and such terminology is often usedto describe many such devices; for example, a solid-state telephoneanswering machine may have no moving parts, yet it is commonly called a“machine” because it performs well-known useful functions.

As used herein, the term “proximal” can have a meaning of closelypositioning one physical object with a second physical object, such thatthe two objects are perhaps adjacent to one another, although it is notnecessarily required that there be no third object positionedtherebetween. In the technology disclosed herein, there may be instancesin which a “male locating structure” is to be positioned “proximal” to a“female locating structure.” In general, this could mean that the twomale and female structures are to be physically abutting one another, orthis could mean that they are “mated” to one another by way of aparticular size and shape that essentially keeps one structure orientedin a predetermined direction and at an X-Y (e.g., horizontal andvertical) position with respect to one another, regardless as to whetherthe two male and female structures actually touch one another along acontinuous surface. Or, two structures of any size and shape (whethermale, female, or otherwise in shape) may be located somewhat near oneanother, regardless if they physically abut one another or not; such arelationship could still be termed “proximal” Or, two or more possiblelocations for a particular point can be specified in relation to aprecise attribute of a physical object, such as being “near” or “at” theend of a stick; all of those possible near/at locations could be deemed“proximal” to the end of that stick. Moreover, the term “proximal” canalso have a meaning that relates strictly to a single object, in whichthe single object may have two ends, and the “distal end” is the endthat is positioned somewhat farther away from a subject point (or area)of reference, and the “proximal end” is the other end, which would bepositioned somewhat closer to that same subject point (or area) ofreference.

It will be understood that the various components that are describedand/or illustrated herein can be fabricated in various ways, includingin multiple parts or as a unitary part for each of these components,without departing from the principles of the technology disclosedherein. For example, a component that is included as a recited elementof a claim hereinbelow may be fabricated as a unitary part; or thatcomponent may be fabricated as a combined structure of severalindividual parts that are assembled together. But that “multi-partcomponent” will still fall within the scope of the claimed, recitedelement for infringement purposes of claim interpretation, even if itappears that the claimed, recited element is described and illustratedherein only as a unitary structure.

All documents cited in the Background and in the Detailed Descriptionare, in relevant part, incorporated herein by reference; the citation ofany document is not to be construed as an admission that it is prior artwith respect to the technology disclosed herein.

The foregoing description of a preferred embodiment has been presentedfor purposes of illustration and description. It is not intended to beexhaustive or to limit the technology disclosed herein to the preciseform disclosed, and the technology disclosed herein may be furthermodified within the spirit and scope of this disclosure. Any examplesdescribed or illustrated herein are intended as non-limiting examples,and many modifications or variations of the examples, or of thepreferred embodiment(s), are possible in light of the above teachings,without departing from the spirit and scope of the technology disclosedherein. The embodiment(s) was chosen and described in order toillustrate the principles of the technology disclosed herein and itspractical application to thereby enable one of ordinary skill in the artto utilize the technology disclosed herein in various embodiments andwith various modifications as are suited to particular usescontemplated. This application is therefore intended to cover anyvariations, uses, or adaptations of the technology disclosed hereinusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this technology disclosedherein pertains and which fall within the limits of the appended claims.

What is claimed is:
 1. A piston for use in a power tool, said pistoncomprising: a top outer surface, a bottom outer surface, and a side wallouter surface that extends between said top and bottom outer surfaces; afirst recess in said side wall outer surface of the piston; and a porousmedia positioned in said first recess along said side wall outer surfaceof the piston, said porous media containing a liquid lubricant.
 2. Thepiston of claim 1, further comprising: a second recess in said side wallouter surface of the piston located at a different position along saidouter surface of the piston; and a perimeter seal positioned in saidsecond recess.
 3. The piston of claim 2, further comprising: a hollowcylinder having an inner surface that is larger in width than said sidewall outer surface of the piston; wherein: said porous media makesphysical contact with said inner surface of said hollow cylinder as thepiston moves through said cylinder in a reciprocating pattern; and saidliquid lubricant is used to lubricate a portion of said inner surface ofsaid hollow cylinder that is proximal to said side wall outer surface ofthe piston as the piston moves through the cylinder.
 4. The cylinderwith piston of claim 3, wherein: said perimeter seal makes physicalcontact with said inner surface of the hollow cylinder as the pistonmoves through said cylinder in a reciprocating pattern; and saidperimeter seal prevents a majority of said liquid lubricant from movingpast said second recess in said side wall outer surface of the piston,during an operating cycle of the piston's reciprocating motion.
 5. Thecylinder with piston of claim 4, further comprising: a driver that is inmechanical communication with the piston; and a guide body that guidessaid driver, and that receives a fastener to be driven by the drivertoward an exit portion of said guide body.
 6. The cylinder with pistonof claim 4, further comprising: a main storage chamber that contains apressurized gas; wherein: said cylinder includes a variable displacementvolume on a first side of the piston that is in pneumatic communicationwith said main storage chamber, and said cylinder includes a variableventing volume on a second, opposite side of the piston that is inpneumatic communication with an outer environment; and said perimeterseal prevents a majority of said liquid lubricant from moving into saidouter environment during an operating cycle of the piston'sreciprocating motion; however, the liquid lubricant is not preventedfrom moving toward said main storage chamber, where it will be re-usedin later operational cycles.
 7. The piston of claim 1, wherein: saidporous media comprises a foam.
 8. The piston of claim 7, wherein: saidfoam comprises air filter material that is resistant to lubricating oil.9. The piston of claim 1, wherein: said porous media comprises open cellfoam having an average cell density of about 60-80 pores per inch. 10.The piston of claim 1, wherein: said liquid lubricant comprises at leastone of: (a) premium ISO Viscosity Grade 68 slideway oil; and (b)lubricating oil with anti-seize grease.
 11. The cylinder with piston ofclaim 3, further comprising: a grease that is applied to the innersurface of said hollow cylinder.
 12. The piston of claim 2, wherein:said piston exhibits a circular cross-section, said porous media isannular in shape, and said seal is annular in shape.
 13. A workingcylinder for a power tool, said working cylinder comprising: a hollowcylinder that includes a movable two-part piston, said cylinderincluding a variable displacement volume on a first side of the piston,and said cylinder including a variable venting volume on a second,opposite side of the piston; said two-part piston comprising: a firstportion made of a metal that is proximal to said second side of thepiston, said first portion being sufficiently small in outer width sothat it does not make physical contact with an inner surface of thehollow cylinder; and a second portion made of a non-metal that isproximal to said first side of the piston, said second portion includingat least one surface that makes slidable contact with said inner surfaceof the hollow cylinder, the at least one surface thereby acting as aslidable bearing surface for the piston.
 14. The working cylinder ofclaim 13, wherein: said first portion of the piston and said secondportion of the piston are constrained with respect to one another in amanner such that said first and second portions always move together asa single piston subassembly.
 15. The working cylinder of claim 13,further comprising: a first recess in said outer surface of the piston;and a porous media positioned in said first recess, said porous mediacontaining a liquid lubricant.
 16. The working cylinder of claim 15,wherein: said porous media comprises a foam.
 17. The working cylinder ofclaim 16, wherein: said foam makes physical contact with an innersurface of the hollow cylinder as the piston moves through said cylinderin a reciprocating pattern; and said liquid lubricant is used tolubricate a portion of said inner surface of the hollow cylinder that isproximal to said outer surface of the piston as said piston movesthrough said hollow cylinder.
 18. The working cylinder of claim 15,further comprising: a second recess in said outer surface of the pistonlocated at a different position along said outer surface of the piston;and a perimeter seal positioned in said second recess.
 19. The workingcylinder of claim 18, wherein: said perimeter seal makes physicalcontact with said inner surface of the hollow cylinder as the pistonmoves through said cylinder in a reciprocating pattern; and saidperimeter seal prevents a majority of said liquid lubricant from movingpast said second recess in said outer surface of the piston, during anoperating cycle of the piston's reciprocating motion.
 20. A piston foruse in a power tool, said piston comprising: a top outer surface, abottom outer surface, and a side wall outer surface that extends betweensaid top and bottom outer surfaces; a first recess in the side wallouter surface of the piston; a first porous media positioned in saidfirst recess; a second recess in said side wall outer surface of thepiston, located at a different position along said side wall outersurface of the piston; a second porous media positioned in said secondrecess; and at least one of said first porous media and second porousmedia containing a liquid lubricant.
 21. The piston of claim 20, furthercomprising: a third recess in said side wall outer surface of the pistonlocated at a different position along said outer surface of the pistonthan said first and second recesses; and a perimeter seal positioned insaid third recess.
 22. The piston of claim 21, further comprising: ahollow cylinder having an inner surface that is larger in width thansaid side wall outer surface of the piston; wherein: said first porousmedia and second porous media make physical contact with said innersurface of said hollow cylinder as the piston moves through saidcylinder in a reciprocating pattern; and said liquid lubricant is usedto lubricate a portion of said inner surface of said hollow cylinderthat is proximal to said side wall outer surface of said piston as thepiston moves through the hollow cylinder.
 23. The cylinder and piston ofclaim 22, wherein: said perimeter seal makes physical contact with saidinner surface of said hollow cylinder as the piston moves through saidcylinder in a reciprocating pattern; and said perimeter seal prevents amajority of said liquid lubricant from moving past said second recess insaid side wall outer surface, during an operating cycle of the piston'sreciprocating motion.
 24. The cylinder and piston of claim 23, furthercomprising: a main storage chamber that contains a pressurized gas;wherein: said cylinder includes a variable displacement volume on afirst side of said piston that is in pneumatic communication with saidmain storage chamber of pressurized gas, and said cylinder includes avariable venting volume on a second, opposite side of the piston that isin pneumatic communication with an outer environment; said perimeterseal prevents a majority of said liquid lubricant from moving into saidouter environment; and said liquid lubricant is not prevented frommoving toward said main storage chamber, where it will be re-used inlater operational cycles.
 25. The cylinder and piston of claim 24,wherein: said first recess and said first porous media are positionedproximal to said first side of the piston; said second recess and saidsecond porous media are positioned proximal to said second side of thepiston; and said third recess and said perimeter seal are positionedbetween said first and second recesses along said outer surface of thepiston.
 26. The cylinder and piston of claim 25, wherein: said firstporous media contains a liquid lubricant upon manufacture, but saidsecond porous media does not contain a liquid lubricant uponmanufacture.
 27. The cylinder and piston of claim 25, wherein: both saidfirst porous media and second porous media contain a liquid lubricantupon manufacture.
 28. The piston of claim 20, wherein: said first porousmedia and second porous media both comprise a foam.
 29. The piston ofclaim 28, wherein: said foam comprises air filter material that isresistant to lubricating oil.
 30. The piston of claim 20, wherein: saidfirst porous media and second porous media both comprise open cell foamhaving an average cell density of about 60-80 pores per inch.
 31. Thepiston of claim 20, wherein: said liquid lubricant comprises at leastone of: (a) premium ISO Viscosity Grade 68 slideway oil; and (b)lubricating oil with anti-seize lubricant.
 32. The cylinder with pistonof claim 22, further comprising: a grease that is applied to the innersurface of said hollow cylinder.
 33. The piston of claim 21, wherein:said piston exhibits a circular cross-section, said first porous mediaand second porous media both are annular in shape, and said seal isannular in shape.